Thus a majority of known chemical and physico
Thus, a majority of known chemical and physico-chemical methods of metallic ions assay has a number of disadvantages, such as a low sensitivity and selectivity, high costs and complexity of the equipment. Therefore, the development of simple cost-effective sensitive methods of quantitative analysis of metallic ions, including Mn and Co, is an important task of analytical chemistry. Thus, metal-ion-dependent T7 High Yield Fluorescein RNA mg , , ,  and catalytic nucleic acids – DNA-zymes or RNA-zymes , , , , , ,  present promising tools for elaboration of such methods. The use of functional nucleic acids as bioelements for the lab-on-a-chip (LOC) biosensors for detection of heavy metal ions have made a great step forward in recent years. A number of metal-ion-dependent DNAzymes and metal-ion-binding DNA structures have been obtained through combinatorial selection and rational design . These molecules have been used as bioselective elements of sensors with fluorescent, colorimetric, electrochemical, and surface Raman detection of correspondent metal ions. For selective sensing metal ions in complex biological samples and live cells, a facile and stable biosensor based on non-biological enantiomer (L-DNAzyme) was proposed by Kue et al. . With its highly sensitivity (with a detection limit down to 11ppt) and selectivity (up to millions-fold) toward specific metal ions, these sensors have been applied for on-site and real-time environmental monitoring, point-of-care medical diagnostics and for in situ cellular imaging . According to the degree of automation and system integration, modern analytical devices may be classified as: microfluidic LOC system, microchip, lateral flow dipstick, personal glucose meter, disc-based analytical platform and microfluidic paper-based (MFPB) sensors , , . MFPB sensors are inexpensive, simple, low-cost, portable, easy to use and usually naked-eye quantitative methods, so these analytical devices are promising for use in developing countries and for field measurements. Analysis of literature data suggests that the further development of novel highly selective and sensitive methods for clinical diagnostics and industry, including enzymatic ones, is necessary. Recently we have demonstrated the possibility to use apoenzyme of Mn-dependent recombinant human liver arginase I as a Mn-sensitive bioelement in biosensor analysis . The bi-enzyme amperometric biosensor based on arginase, isolated from the recombinant yeast cells, and commercial urease revealed a high sensitivity to Mn-ions (9200±20AMm) and a low detection limit (0.15μM). Arginase I (EC 126.96.36.199; L-arginine amidinohydrolase) is an Mn containing enzyme of the urea cycle. It catalyses the final cytosolic reaction of urea formation in the mammalian liver — the conversion of arginine to ornithine and urea. Arginase I (further – arginase) has recently been considered as a prospective pharmaceutical in enzymotherapy for some kinds of auxotrophic cancers for L-arginine (further - Arg) as well as an analytical instrument for assay of the own substrate — Arg . In this paper, we describe the development of a novel enzymo-chemical method for differential Mn and Co ions determination and its application on the real samples of wastewaters. The proposed method, based on apoenzyme of recombinant arginase, revealed a high sensitivity and selectivity to Mn and Co ions. The binding of Mn or Co with apoenzyme of arginase, at experimentally estimated optimal pH values, induces holoenzyme reconstruction, followed by recovering arginase activity and generation of urea from Arg in arginase-catalysed reaction at different pH-values: 9,1 and 7,1 for Mn and Co, respectively. Analytical signal is the result of the formation of a stable product between urea and 2,3-butanedione monoxime (DMO) in an acidic medium . The resulted compound can be spectrophotometrically and fluorometrically monitored. The advantages of the proposed method are the simplicity and the fastness (if compared to HPLC and other instrumental methods) of analytic procedure. Being highly sensitive, selective, valid and cost-effective, the proposed analytical method will be promising for Mn and Co ions assay in different fields of science and technology, including environmental chemistry, plant and animal biochemistry, nutrition, and medicine.